The high-density digital-versatile disc (HD-DVD) uses an eight to twelve modulation (ETM) technique. That is, 8-bit symbols (i.e., user bytes or data words) are converted into 12-bit code words that are stored on the disc.
FIG. 1 is a schematic diagram illustrating a related art modulating and demodulating method. As shown in FIG. 1, an input code IC (for example, a data word) is converted into an output code OD (for example, a code word) according to a table 101. A factor Sn called state or case is also determined according to the input code IC, the output code OD, and the table 101. For HD-DVD modulation, input code IC represents an 8-bit data word, output code represents a 12-bit code word, and table 101 is a preset modulation table; however, for HD-DVD demodulation, input code IC represents a 12-bit code word, output code represents an 8-bit data word, and table 101 is a preset demodulation table.
Taking HD-DVD encoding for example, this modulation table requires 256 (8-bit)×3 (12-bit) entries. FIG. 2 illustrates a portion of a related art modulation table. As shown in FIG. 2, if a data word needs to be transformed to a code word, the location of the data word in the modulation table must first be confirmed, and then the code word corresponding to the data word is determined in view of the state value. Taking data word 1D (hex) for example, if the state is 0, then the codeword is 100010 000101(binary); if the state is 1, the codeword is 010000 000101(binary); and if the state is 2, the codeword is 010000 000101(binary).
The bit asterisk “*” in the code conversion table FIG. 2 shows that the bit is a merging-bit. Some code words of the conversion table have merging-bit in their LSB. The merging-bit is set to 0(binary) or 1(binary) by code connector according to channel bit following itself. If the following channel bit is 0b, the merging-bit shall be set to 1b. If the following channel bit is 1b, the merging-bit shall be set to 0b. 
The bit sharp “#” in the conversion table FIG. 2 shows that the bit is a DSV (Digital Sum Values) control bit. The DSV control bit is determined by executing DC component suppression control by DSV controller. The purpose is to minimize the absolute value of the accumulated DSV.
For HD-DVD decoding, the demodulation table requires 355 (12-bit)×3 (8-bit) entries. FIG. 3 illustrates a portion of a related art demodulation table. As shown in FIG. 3, if a code word needs to be transformed to a data word. The location of the code word must first be confirmed, and then the data word corresponding to the code word is determined in view of the case value. Taking code word 000010 000000 for example, if the case is 1, then the data word is C0; if the case is 2, then the data word is E; if the case is 3, then the data word is C1.
However, the modulation table shown in FIG. 2 and the demodulation table shown in FIG. 3 are not complete. The actual modulation table and demodulation table dimensions are many times greater than that shown in the modulation table in FIG. 2 and the demodulation table in FIG. 3. Thus, the modulation and demodulation tables are difficult to implement and consume a large space because of a high channel bit rate. Therefore, a system or method for solving this problem is needed.